1. Field of the Invention
This invention relates to a viewer for eliminating dead zones around a medium or large size truck or a construction vehicle to ensure safety in driving.
2. Description of the Prior Art
The prior art uses a convex mirror method, a TV method, or a sensor method using radio waves. The convex mirror method has disadvantages that images are extremely distorted, the effective observation zone is narrow, and a large convex mirror installed at the back of a vehicle for backward observation protrudes from the vehicle body and is not suited to safe operation.
The TV method has problems in that it is expensive, the camera may be stolen, and a room for an image receiver is required.
The sensor method using radio waves also has problems that result from indirect sensing of obstacles, such as faults in the equipment, the procedure for sensitivity adjustment, and erroneous reaction due to too sharp sensitivity.
To solve these problems, techniques indicated in Japanese Utility Model Laid-Open 55-15118 and 59-133340, and Japanese Patent Laid-Open 60-213534 were proposed. However, the techniques result in incur problems such as the viewer protruding from the vehicle body, causing danger during running, and the possibility of the viewer being damaged or soiled.